The present invention relates to an ink jet system printer of the charge amplitude controlling type and, more particularly, to an interpolation dot control system in an ink jet system printer.
Generally, an ink jet system printer of the charge amplitude controlling type includes a carriage which is driven to travel in front of a record receiving paper in the lateral direction. The carriage carries a printer head including a nozzle and a charging tunnel. An electro-mechanical transducer is attached to the nozzle for issuing ink droplets at a given frequency. A charging operation is conducted by the charging tunnel in accordance with the print information to charge the ink droplet to a desired level. A pair of deflection electrodes are mounted on the carriage for deflecting the charged ink droplets in the vertical direction, thereby printing desired symbols on the record receiving paper in a dot matrix fashion. Ink droplets not contributing to the actual printing operation are neither charged nor deflected, and collected by a beam gutter disposed between the deflection electrodes and the record receiving paper.
In such an ink jet system printer of the charge amplitude controlling type, the printing quality is greatly influenced by the speed of the travelling carriage because the lateral position in the dot matrix pattern is determined by the location of the travelling carriage. However, it is difficult to strictly control the speed of the travelling carriage over one line of the printing operation to render this speed uniform. The speed of the travelling carriage normally varies during the one line printing due to, for example, the drift phenomenon. The variation of the speed of the travelling carriage appears in the printed pattern as a variation in the width of, for example, the printed characters.
Accordingly, an object of the present invention is to provide a print control system in an ink jet system printer of the charge amplitude controlling type, which ensures stable printing operation even when the speed of the travelling carriage varies during one line of the printing operation.
Another object of the present invention is to provide an interpolation dot control system which functions to compensate for the variation in the speed of the travelling carriage.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, a detection system is provided for detecting the location of the travelling carriage. The detection system develops a timing signal when, for example, the travelling carriage reaches the respective character print position. A counter system is provided for counting the number of ink droplets developed between the adjacent two timing signals. The thus obtained count information is compared with a reference number, and the ratio of the actually applied number of ink droplets to the reference number (the so-called interpolation dot ratio) is determined in response to the comparison result. More specifically, when the count number of the ink droplets is greater than the reference number, this indicating the fact that the speed of the travelling carriage is lower than a desired level, the number of the interpolation dots is increased to prevent the character width from being narrowed. In such an ink jet system printer, the first dot position of the individual character is determined by the timing signal developed from the carriage position detection system .